The effect of flow rate and agitation technique on irrigant extrusion ex vivo

Aim To evaluate (i) the effect of irrigant flow rate, needle type, needle insertion depth and apical constriction diameter and (ii) the effect of ultrasonic, sonic and manual dynamic agitation on irrigant extrusion using a recently introduced method. Methodology Thirty-two human teeth with a straight root canal were prepared to size 35, 0.06 taper and assigned to group A or B. The apical constriction diameter was 0.15–0.25 mm. Specimens were mounted on a plastic vial filled with distilled water to simulate a periapical lesion. A point-conductivity probe was used to determine the volume of irrigant extruded into the vial. Within group A, NaOCl was delivered at 0.14 or 0.26 mL s−1 by an open-ended or a closed-ended needle at 1 or 3 mm short of working length (WL). In group B, NaOCl was agitated at high or low power either by an ultrasonically or sonically oscillating instrument inserted at 1 or 3 mm short of WL or by manual push–pull strokes of a gutta-percha cone. Results were analysed by repeated-measures anovas, at 0.05 significance. Results An increase in the flow rate resulted in increased extrusion (P   0.454). Manual dynamic agitation extruded significantly more irrigant than sonic and ultrasonic agitation (P < 0.001). Conclusions Irrigant flow rate, needle type and insertion depth and agitation technique had a significant effect on extrusion.